Glock, H.-W.; Dürr, V.; Glöckner, F.; Ries, M.; Sharples-Milne, E.; Tannert, M.; Wolk, D.; Vélez, A.; Knobloch, J.: New collimating shielded bellow for the connection of superconducting rf cavities in a high current storage ring. Physical Review Accelerators and Beams 26 (2023), p. 04320/1-15
10.1103/PhysRevAccelBeams.26.043201
Open Access Version
Abstract:
The implementation of concatenated superconducting rf cavities into high current storage rings raises the demand for appropriate beam pipe bellows. In order to compensate for length variations of the cavities due to thermal shrinkage and tuning, a mechanically soft element is required. It also should be of the least interaction with the beam to reduce the deposition of electromagnetic field energy, i.e., wakefields. Even in close neighborhood to high level cavity fields, parasitical Ohmic losses need to be minimized in order not to exceed cryogenic cooling capabilities. Overall construction length is an issue since real estate is strongly limited in between the existing magnetic lattice. The device needs to be compatible with cryogenic and ultrahigh vacuum conditions. The paper describes such a device as it was developed and tested in the framework of the Variable pulse length Storage Ring (VSR) Demo project, pursued at Helmholtz-Zentrum Berlin as a possible upgrade of the synchrotron light source BESSY II. It is denoted as Collimating Shielded Bellow, named such since it furthermore acts as an actively cooled synchrotron light collimator. The mechanical, electrodynamical, and thermal designs are presented. Particular attention is paid to the testing setup and the vacuum performance with the beam observed during extended testing periods in BESSY II.